1. Field of the Invention
The invention relates to a steering system and a coupling wire that is used for the steering system.
2. Description of Related Art
As a vehicle steering system, there is known a telescopic-type steering system that adjusts the position of a steering wheel in the vehicle longitudinal direction by extending or contracting a steering column based on the body size and the driving posture of a driver. In a telescopic-type steering system, generally, a steering column is formed by joining an upper tube with a lower tube and a telescopic steering shaft is housed in the steering column. For example, Japanese Patent Application Publication No. 2010-111299 (JP 2010-111299 A) describes a conventional telescopic-type steering system.
To install a telescopic-type steering system in a vehicle, first, a steering column is assembled from an upper tube and a lower tube, and then the steering column is installed in the vehicle. At this time, the relative displacement between the upper tube and the lower tube along the axial direction of a steering shaft may be caused. Therefore, the relative positions of the upper tube and the tower tube may be greatly changed during the installation work, which reduces the work efficiency. In recent years, the weight of steering columns has been increasing, which further increases the difficulty in the work of installing a steering column in a vehicle. Therefore, techniques for improving the efficiency of the work of installing a steering column in a vehicle have been expected.
In order to improve the efficiency of the installation work, there may be employed, for example, a technique in which an upper tube and a lower tube are coupled to each other by a metal wire and, in this state, a steering column is installed in a vehicle. According to the technique, it is possible to more easily perform the work of installing the steering column in the vehicle because the wire restricts the relative displacement between the upper tube and the lower tube. However, if the wire is kept unremoved even after the steering column is installed in the vehicle, electricity may be passed through the wire. In, for example, a steering system of an electric power steering type, components such as an electric motor and a control circuit are installed on a lower tube and therefore electricity that is supplied from a battery to the lower tube may be passed through a wire. If electricity is passed through the wire, the temperature of the wire becomes high, which may exert adverse effects on nearby components.